en quatre parties VS en quatre morceux

If the exercise is to teach what the correct phrase is for translating:

You are going to divide the cake in four parts.

Vous allez diviser le gâteau "en quatre parties" - should be correct. However, that response was marked incorrect. With the correction:
"en quatre morceux" (pieces), which is not what was asked for.
The next time the request for the translation appeared, I entered "en quatre morceux" and it was marked incorrect with the correction: 'en quatre parties".

It would be very helpful to those of us who are trying to learn French if Duolingo would ask specifically what we are supposed to respond (parts or pieces) and be consistent.